(Mark Lennihan/AP)

On Monday, Taco Bell became the latest fast-food company to announce its plan to use only cage-free eggs. The commitment comes in the wake of similar announcements made by virtually all of its competitors, suggesting that ignoring efforts to ensure animal welfare is increasingly not a viable strategy in the industry.

"This is enormous news," said Leah Garces, who is the U.S. director of Compassion in World Farming, an animal rights group. "Especially given the timeline, which will be the fastest yet."

The promise, which the chain will carry out by the end of 2016, is certainly impressive in this respect. No other company, after all, has committed to do the same in fewer than five years. What's more, several, including McDonald's, have talked about the switch as a 10-year goal.

It also stands to be impactful. Taco Bell, which has more than 6,000 restaurants throughout the United States, sells close to 150 million eggs each year, which could be a boon for the cage-free egg industry. The shift will improve the lives of more than 500,000 hens, according to estimates by the Humane Society of the United States.

"Implementing this change at record pace underscores that we are always listening and responding to our customers, while doing what is right for our business," Brian Niccol, chief executive of Taco Bell Corp., said in a statement.

Taco Bell's announcement follows growing criticism of the company's refusal to change its supply chain. At a time when animal rights have become an issue more people care about, the Mexican-food-themed eatery has been exceptionally slow to join the movement. This month, a Washington Post article highlighted the chain's silence on animal welfare. A petition on Change.org pleading for Taco Bell to go cage-free also gathered more than 166,000 signatures.

How exactly it will manage to change the entirety of its egg supply in a single year is unclear. The company pointed to its "large yet flexible infrastructure" as the key but said nothing about whether the expedited change will lead to any upticks in price.

For a time, it seemed that Yum Brands, the parent company that owns Taco Bell, Pizza Hut and KFC, might remain steadfast in its decision not to follow the lead of companies like Chipotle and Panera, which have helped pioneer the fast-food world's increased commitment to animal welfare.

The U.S. food system isn't currently equipped to supply the amount of humanely raised animal products the fast-food industry serves, raising questions about whether it's even possible at this moment for companies like Taco Bell to source something like cage-free eggs. Humane farming practices also tend to be less efficient, and, therefore, more costly. While many fast-food outlets can pass some of the added cost on to consumers, Taco Bell, which relies on cheap prices to woo customers, labors over every extra penny it has to charge. 

The chances of Taco Bell committing to use only cage-free eggs seemed particularly unlikely given how the promise might affect its breakfast menu, which was first introduced last year. The strategy has centered around novelty — there was a waffle taco, then a biscuit taco — and convenience: All of their offerings are easily eaten on the go, many with only a single hand. But its appeal has been predicated on price. Switching to cage-free eggs could compromise that, and with it, the chain's chance of elbowing out some room in the fast-food breakfast space.

The shift in the company's policy points to a fundamental change in the fast-food world. The industry, which has long prioritized price, can probably no longer afford to do so at the expense of animal welfare. Fast casual restaurants, which have shown that charging a little more for something customers feel good about buying can be a viable business, have inspired a domino effect, nudging almost every major fast-food company to take steps to fix how they get their food.

And it's something of a self-perpetuating process. The more companies there are that demand cage-free eggs, the more producers there will have to be to provide them; the more producers, the more supply; and the more supply, the lower the prices. Slowly, but surely, it becomes easier for more fast-food companies — even the most price-sensitive ones — to supply cage-free eggs, too.

Taco Bell is the last of the major U.S. fast-food brands to announce a switch to cage-free eggs, but it will be the first to implement the change. By the time McDonald's, which uses more than 2 billion eggs in the United States each year, or roughly 5 percent of all eggs produced in the country, makes good on its promise in 2025, the egg industry will look remarkably different. Supermarket shelves probably will, too.